One ROM to rule them all.

Software Defined Retro ROMs

July 19, 2025 by 2 Comments

Here’s something fun from our hacker [Piers]: Software Defined ROMs.

In this series of three videos, [Piers] runs us through what a software defined ROM is, how to make them, and then how to use them.

As [Piers] explains, one frustration a retro technician will face is a failed ROM chip. In the era he’s interested in, there are basically three relevant kinds of ROM chip, all 24-pin Dual Inline Package (DIP):

  • 2364 ROM chip: 8KB; 1x chip-select line
  • 2332 ROM chip: 4KB; 2x chip-select lines
  • 2316 ROM chip: 2KB; 3x chip-select lines

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SymbOS Is A Funhouse Mirror Look At A Future That Never Was

July 19, 2025 by 4 Comments

The Z80 might be decades obsolete and a few years out of production, but it’s absolutely a case of “gone but not forgotten” in the hacker world. Case in point is SymbOS, a multitasking OS for Z80 machines by Amstrad, Sinclair, and the MSX2 family of computers that updated to version 4.0 earlier this year.

The best way to describe SymbOS is like looking at an alternate reality where Microsoft created Windows 95 ten years early to put on the MSX instead of the BASIC they were paid to provide. SymbOS 4.0 comes even further into alignment with that design language, with a new file explorer that looks a lot like Windows Explorer replacing (or supplementing) the earlier Midnight Commander style utility in version 3.

Thanks to the preemptive multitasking, you can listen to tracker music while organizing files and writing documents, and even play a port of DOOM. Chat with your friends on IRC while watching (low res) videos on SymboVid. If you’re looking for productivity, all the old business software written for CP/M can run in a virtual machine. There’s even an IDE if you can stand the compile times on what is, we have to remember, an 8-bit, 1980s machine. It’s hard to remember that while watching the demo video embedded below.

The operating system supports up to 1024kb of RAM (in 64kb chunks, of course) and file systems up to 2 TB, which is an absolutely bonkers amount of space for this era’s machines.  One enterprising dev has even got his CPC talking to ChatGPT, if that’s your jam. You can try SymbOS for free online on an MSX emulator, or toss it onto a spare Raspberry Pi.  If you’re feeling adventurous, there’s a port in the works for the Isetta TLL retrocomputer.

This isn’t the first modern OS we’ve featured for the Z80, the processor which will live forever in our hearts and tapeouts.

Thanks to [Manuel] for the tip.

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PicoGUS Adds CD-ROM Emulation To ISA Bus

July 19, 2025 by 17 Comments

Everything fails eventually, but moving parts fail fastest of all– and optical drives seemingly more than others, at least in our experience. Even when they work, vintage drives often have trouble with CD-R, and original media isn’t always easy to find. That’s why it’s so wonderful that [polpo]’s RP2040 ISA card, the PicoGUS 2.0, now supports CD-ROM emulation.

We covered PicoGUS when it first appeared as an ISA sound card,  and make no mistake, it can still emulate sound cards for retro-PC beeps and boops. It’s not just the Gravis Ultrasound (GUS) from which the project took its name, but Sound Blaster 2.0, MPU-401 for MIDI, Tandy 3-voice, and CMS/GameBlaster are all soft options. Like most sound cards back in the day, PicoGUS provides game port support as well.

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Punch Card Controlled Cyberdeck Lives In 80s Toy

July 19, 2025 by 4 Comments

Have you ever seen a toy and said “That wants to be a deck”? [Attoparsec] did, when his eyes fell upon the Little Talking Scholar, a punch card driven toy from the 1980s. It’s now a punch card driven cyberdeck.

The punch card interface on the toy is only six bits, but sixty-four application cards are probably more than parents would have wanted to keep track of in 1989. Originally, they cued up simple matching games on an anonymous epoxy-coated microprocessor; after [Attoparsec]’s surgery, they do the same thing, cuing up custom Python applications on the Raspberry Pi Zero he’s implanted into this thing.

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Elegoo Rapid PETG Vs PETG Pro: Same Price, Similar Specs, Which To Buy?

July 19, 2025 by 10 Comments

Even within a single type of FDM filament there is an overwhelming amount of choice. Take for example Elegoo’s PETG filament offerings, which include such varieties like ‘Pro’ and ‘Rapid’. Both cost the same, but is there a reason to prefer one over the other, perhaps even just for specific applications? To test this, [Dr. Igor Gaspar] over at the My Tech Fun YouTube channel bought some spools of these two filaments and subjected both to a series of tests.

Obviously, the Rapid filament is rated for higher extrusion speeds – <270 vs <600 mm/s – while the website claims a higher required nozzle temperature that confusingly does not match those listed on the spool. There are quite a few differences in the listed specifications, including the physical and mechanical properties, which make it hard to draw any immediate conclusions. Could you perhaps just use Rapid PETG and forget about the Pro version?

Test objects were printed with a Bambu Lab P1P with an AMS unit. After calibrating the ideal temperature for each filament, a tensile break test gave a win to the Rapid PETG, followed by a layer adhesion test win. This pattern continued across further tests, with Rapid PETG either matching or beating the Pro PETG.

There are only two advantages of the Pro version that can be seen here, which are less moisture sensitivity and  stringing risk, and you of course get the luxury cardboard spool with the closed edges. Whether that’s enough to make you go ‘Pro’ remains to be seen, of course.

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Neon Lamp Detects Lightning Strikes

July 19, 2025 by 9 Comments

For as mysterious, fascinating, and beautiful as lightning is at a distance, it’s not exactly a peaceful phenomenon up close. Not many things are built to withstand millions of volts and tens to hundreds of thousands of amps. Unsurprisingly, there’s a huge amount of effort put into lightning protection systems for equipment and resources that need to be outside where thunderstorms sometimes happen. Although most of us won’t be building personal substations, church steeples, or city-scale water towers in our backyards, we might have a few radio antennas up in the air, so it’s a good idea to have some lightning protection and possibly an alert system like [Joe] built.

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A photo of the circuitry in its case

GarageMinder: Automatic Garage Door

July 19, 2025 by 12 Comments

After getting a new car, [Solo Pilot] missed the automatic garage door opening and closing system their old car had. So they set about building their own, called GarageMinder. On the project page you will find a bill of materials, schematics, and some notes about the approach taken in various versions of the software. [Solo Pilot] also made the software available.

The basic hardware centers around a Raspberry Pi Zero W, but there are plans to switch to an ESP32. From the car side of things there are built-in continuous Bluetooth Low Energy (BLE) advertisement broadcasts, which the Raspberry Pi can detect. Building a reliable system on top of these unreliable signals is difficult and you can read about some of the challenges and approaches that were taken during development. This is a work in progress and additional techniques and approaches are going to be trialed in future.

If you’re interested in Bluetooth garage door openers be sure to read about using a Bluetooth headset as a garage door opener for your Android device.